public bool TryGet(object key, out object value)
{
object o;
readWriteLock.AcquireReaderLock(MAX_LOCK_WAIT);
try {
if (untimedStorage.ContainsKey(key))
{
value = untimedStorage[key];
return(true);
}
LockCookie lc = readWriteLock.UpgradeToWriterLock(MAX_LOCK_WAIT);
try {
if (timedStorageIndex.ContainsKey(key))
{
TimedCacheKey tkey = timedStorageIndex[key];
o = timedStorage[tkey];
timedStorage.Remove(tkey);
tkey.Accessed();
timedStorage.Add(tkey, o);
value = o;
return(true);
}
else
{
value = null;
return(false);
}
}
finally { readWriteLock.DowngradeFromWriterLock(ref lc); }
}
finally { readWriteLock.ReleaseReaderLock(); }
}
public object Get(object key)
{
object o;
readWriteLock.AcquireReaderLock(MAX_LOCK_WAIT);
try {
if (untimedStorage.ContainsKey(key))
{
return(untimedStorage[key]);
}
LockCookie lc = readWriteLock.UpgradeToWriterLock(MAX_LOCK_WAIT);
try {
if (timedStorageIndex.ContainsKey(key))
{
TimedCacheKey tkey = timedStorageIndex[key];
o = timedStorage[tkey];
timedStorage.Remove(tkey);
tkey.Accessed();
timedStorage.Add(tkey, o);
return(o);
}
else
{
throw new ArgumentException("Key not found in the cache");
}
}
finally { readWriteLock.DowngradeFromWriterLock(ref lc); }
}
finally { readWriteLock.ReleaseReaderLock(); }
}
/// <summary>
/// Purges expired objects from the cache. Called automatically by the purge timer.
/// </summary>
private void PurgeCache(object sender, System.Timers.ElapsedEventArgs e)
{
// Note: This implementation runs with low priority. If the cache lock
// is heavily contended (many threads) the purge will take a long time
// to obtain the lock it needs and may never be run.
System.Threading.Thread.CurrentThread.Priority = ThreadPriority.BelowNormal;
// Only let one thread purge at once - a buildup could cause a crash
// This could cause the purge to be delayed while there are lots of read/write ops
// happening on the cache
if (!Monitor.TryEnter(isPurging))
{
return;
}
try {
readWriteLock.AcquireWriterLock(MAX_LOCK_WAIT);
try {
List <object> expiredItems = new List <object>();
/*
* DateTime startTime = DateTime.Now;
* System.Console.WriteLine("Purge " + " started at " + startTime.ToLongTimeString());
*/
foreach (TimedCacheKey timedKey in timedStorage.Keys)
{
if (timedKey.ExpirationDate < e.SignalTime)
{
// Mark the object for purge
expiredItems.Add(timedKey.Key);
}
else
{
break;
}
}
foreach (object key in expiredItems)
{
TimedCacheKey timedKey = timedStorageIndex[key];
timedStorageIndex.Remove(timedKey.Key);
timedStorage.Remove(timedKey);
}
/*
* DateTime endTime = DateTime.Now;
* System.Console.WriteLine("Purge completed at " + endTime.ToLongTimeString());
* System.Console.WriteLine("Time taken to complete purge was " + TimeSpan.FromTicks(endTime.Ticks - startTime.Ticks));
*/
}
catch (ApplicationException ae) {
// Unable to obtain write lock to the timed cache storage object
System.Console.WriteLine("Unable to complete cache purge, could not get writer lock.");
}
finally {
readWriteLock.ReleaseWriterLock();
}
}
finally { Monitor.Exit(isPurging); }
}
public bool Update(object key, object value, DateTime expiration)
{
// Synchronise access to storage structures. A read lock may
// already be acquired before this method is called.
bool LockUpgraded = readWriteLock.IsReaderLockHeld;
LockCookie lc = new LockCookie();
if (LockUpgraded)
{
lc = readWriteLock.UpgradeToWriterLock(MAX_LOCK_WAIT);
}
else
{
readWriteLock.AcquireWriterLock(MAX_LOCK_WAIT);
}
try {
if (untimedStorage.ContainsKey(key))
{
untimedStorage.Remove(key);
}
else if (timedStorageIndex.ContainsKey(key))
{
timedStorage.Remove(timedStorageIndex[key]);
timedStorageIndex.Remove(key);
}
else
{
return(false);
}
TimedCacheKey internalKey = new TimedCacheKey(key, expiration);
timedStorage.Add(internalKey, value);
timedStorageIndex.Add(key, internalKey);
return(true);
}
finally {
// Restore lock state
if (LockUpgraded)
{
readWriteLock.DowngradeFromWriterLock(ref lc);
}
else
{
readWriteLock.ReleaseWriterLock();
}
}
}
public bool Add(object key, object value, TimeSpan slidingExpiration)
{
// Synchronise access to storage structures. A read lock may
// already be acquired before this method is called.
bool LockUpgraded = readWriteLock.IsReaderLockHeld;
LockCookie lc = new LockCookie();
if (LockUpgraded)
{
lc = readWriteLock.UpgradeToWriterLock(MAX_LOCK_WAIT);
}
else
{
readWriteLock.AcquireWriterLock(MAX_LOCK_WAIT);
}
try {
// This is the actual adding of the key
if (timedStorageIndex.ContainsKey(key))
{
return(false);
}
else
{
TimedCacheKey internalKey = new TimedCacheKey(key, slidingExpiration);
timedStorage.Add(internalKey, value);
timedStorageIndex.Add(key, internalKey);
return(true);
}
}
finally {
// Restore lock state
if (LockUpgraded)
{
readWriteLock.DowngradeFromWriterLock(ref lc);
}
else
{
readWriteLock.ReleaseWriterLock();
}
}
}
public bool Update(object key, object value, TimeSpan slidingExpiration)
{
// Synchronise access to storage structures. A read lock may
// already be acquired before this method is called.
bool LockUpgraded = readWriteLock.IsReaderLockHeld;
LockCookie lc = new LockCookie();
if (LockUpgraded)
{
lc = readWriteLock.UpgradeToWriterLock(MAX_LOCK_WAIT);
}
else
{
readWriteLock.AcquireWriterLock(MAX_LOCK_WAIT);
}
try
{
if (untimedStorage.ContainsKey(key))
{
untimedStorage.Remove(key);
}
else if (timedStorageIndex.ContainsKey(key))
{
timedStorage.Remove(timedStorageIndex[key]);
timedStorageIndex.Remove(key);
}
else
{
return false;
}
TimedCacheKey internalKey = new TimedCacheKey(key, slidingExpiration);
timedStorage.Add(internalKey, value);
timedStorageIndex.Add(key, internalKey);
return true;
}
finally
{
// Restore lock state
if (LockUpgraded)
{
readWriteLock.DowngradeFromWriterLock(ref lc);
}
else
{
readWriteLock.ReleaseWriterLock();
}
}
}
public bool Add(object key, object value, DateTime expiration)
{
// Synchronise access to storage structures. A read lock may
// already be acquired before this method is called.
bool LockUpgraded = readWriteLock.IsReaderLockHeld;
LockCookie lc = new LockCookie();
if (LockUpgraded)
{
lc = readWriteLock.UpgradeToWriterLock(MAX_LOCK_WAIT);
}
else
{
readWriteLock.AcquireWriterLock(MAX_LOCK_WAIT);
}
try
{
// This is the actual adding of the key
if (timedStorageIndex.ContainsKey(key))
{
return false;
}
else
{
TimedCacheKey internalKey = new TimedCacheKey(key, expiration);
timedStorage.Add(internalKey, value);
timedStorageIndex.Add(key, internalKey);
return true;
}
}
finally
{
// Restore lock state
if (LockUpgraded)
{
readWriteLock.DowngradeFromWriterLock(ref lc);
}
else
{
readWriteLock.ReleaseWriterLock();
}
}
}
